It's obvious you have a cpu bottleneck or some other problem going on.
With an E8500 @ 3.8GHz? I doubt it.
There is certainly a problem here, and while I am not sure what it is, I strongly doubt it is the CPU.
@Toyota:
Some obvious things, but for the sake of thoroughness:
1.) Did you just swap the card in and then updated to new drivers?
2.) Did you remove the old drivers first and run DriverSweeper, before using the latest driver on your new card?
3.) Or was this actually a complete reinstall of the OS (unnecessary for new video cards, but if you timed your purchase with a new OS install, it would nullify the suspicion on driver issues)?
I needed to ask only because I do not believe it mentioned in the thread yet, and on the off chance that it might actually be useful.
Whatever the case, if you do not end up returning the card and it makes it to your i5 quad, it would be very helpful to post results of those as well.
Thanks.